Method and apparatus for manufacturing wallboard



April 1 1941- J. K. DUNCAN 2.238.017

METHOD AND ABPARATUS FOR MANUFACTURING WALLBOARD Filed Oct. 23, 1937 Patented Apr. 8, 1941 METHOD AND APPARATUS FOR MANU- FAOTURING WALLBOARD James K. Duncan, Chicago, Ill., assignor to United States Gypsum Company, Chicago, 111., a corporation of Illinois Application" October 23, 1937, Serial No. 170,513

13 Claims.

' sheet, of wallboard having a cementitious or composition core, and paper or fibrous liners or cover "sheets, is, of course, well known. It is likewise well known to produce, in a continuous manner, such wallhoard having beveled or depressed longitudinal edges, so that when the wallboards are assembled in a wall structure a more perfect joint between the boards may be formed by applying suitable joining tape and sealing cement to the recess formed by adjacent edges of the board.

While a'similar advantage is to be found in wallboards having their transverse ends beveled or depressed, particularly when the boards are to be erected with the long, dimensional boards horizontal, no entirely satisfactory method has heretofore been proposed for manufacturing such beveled or recessed-end boards.

It has been proposed to form such recessed-end boards by depressing portions of the board after 3 the board has been cast or formed. This procedure is not entirely satisfactory, since the pressing operation is usually detrimental to the core of the board. It has likewise been proposed to produce such recessed-end boards by forming parallel rows of projections in the outer surface of one of the cover sheets by punching the cover sheet before the board is formed and severing the continuous board stream between the rows of projections after the board is formed. It will be apparent that boards formed by this latter method have a series of projections spaced along the depressed or beveled portions, and that these projections seriously interfere with the application of joining tape and sealing cement when a wall structure is being erected from the boards. Numerous other objections are also found in recessed-end boards of this typehaving projections along the recessed-end portions.

It is a further object of my invention to provide an improved method and apparatus for forming. in a continuous manner.- wallboards of this character having-recessed-end portions.

In carrying out my invention in one form, one

of the cover sheets is embossed or creased prior to my invention;

the formation of the board to provide spaced. transversely extending projections on one surface of the board, which projections are effective to space adjacent portions of the cover sheet and of the composition core from the supports therefor during the formation of the board, and during the passage of the board over the setting conveyors. After the core of the board has set, the continuous board stream issevered along opposite sides of the projections entirely to remove the projection from the board and to provide boards of predetermined length having uniformly beveled or recessed-end portions. If desired the continuous board stream may be severed along thecenter lines of the projections and the ends of the boards thus formed may be then trimmed to provide uniform beveled ends.

As a further aspect of my invention, means are provided for applying to the projections, before the application of the plastic mass or core, a suitable stiffening medium so as to prevent deformation of the projections during the board-forming operation. This stiffening medium may have moisture-proofing characteristics if desired. In certain cases the embossing of the cover sheet is carried out in such a manner that the depth of the projections is less than the thickness of the cover sheet, so that a continuous layer of fiber is provided to improve the resistance of the projections to deformation when subjected to tension or pressure. In forming wallboards of the type in which one of the cover sheets is folded around the edges of the plastic mass or core, the projection or embosture extends only across that portion of the cover sheet which is to form the bottom surface of the board so that no creasing or embossing is effected in the portions of the cover sheet to be folded about the core.

Fora more complete understanding of my in- I vention reference should now be had to the drawing, in which:

Figure 1 is a somewhat diagrammatic representation of boardforming apparatus embodying Fig. 2 is a fragmentary perspective view of a portion of the scored or creased cover sheet;

Fig. 3 is a fragmentary side view of a. section of i the continuous board stream before the severing operation has been performed;

Fig. 4 is a fragmentary elevational view of a.

recessed-end board formed in accordance with my invention:

Fig. 5 is a detail view of a portion of the scored sheet shown in Fig. 2:

Fig. 6 is a similar detail View of aportlon of a cover sheet formed in. accordance with a further embodiment of my invention; and

Fig. 7 is a transverse sectional view of a scored cover sheet constituting a further embodiment of my invention.

Referring now to Fig. 1 of the drawing, I-have shown my invention as applied to a board-forming apparatus comprising a pair of embossing rolls I and II, respectively, provided with intermeshing projections I2 and recesses I3 for engaging a fibrous cover sheet or liner It as it is continuously advanced to the forming means of the apparatus. The embossing rolls Ill and II are driven in synchronism by suitable means, not shown, and are arranged to emboss or crease the sheet ll at predetermined intervals so as to provide projections I extending outwardly from one surface of the sheet. As shown best in Fig. 2, these projections I5 extend transversely entirely across the cover sheet I 4 and are preferably channel-shaped, the side walls of the projections extending substantially at right angles to the' surface of the cover sheet.

As shown, the projections I2 and the recesses I3 are so arranged that suflicient space is left between each projection and its cooperating recess to permit the cover sheet I4 to pass therebetween with substantially a pressure fit, so that the cover sheet is crimped into the sharp corner projection I5. In some cases it may be desirable to coat the inner surface of the projection I5 with a suitable moisture resisting and stiffening medium such as lacquer or wax, and for carrying out thisrcoating operation I provide a coating wheel I6 supported on a movable arm II and arranged sequentially to engage the projections I2 on the scoring roll I0 so as to apply the stiffening medium to the projections. As shown, the roll I6 is supported so as to engage the periphery of a cooperating roll I8 which is rotatable in a suitable reservoir I9 containing a bath of suitable stiffening medium. The feature of applying stiffening medium is of particular importance where very thin cover sheets or-liners are used which would otherwisebe incapable of supporting the plastic mass when the thin sheet- Y is moistened.

After the cover sheet I4 has been provided with projections or embostures as described above, it passes over a casting table or support 23 and a plastic mass 2| is applied to the upper surface thereof from any suitable source of supply, as for example the supply spout 22, the plastic mass 2| preferably being gypsum plaster .or other suitable composition material in a plastic or manageable state. After the plastic mass 2| is applied to the upper surface of the sheet ll, the plastic mass and the sheet I4 pass between a pair of forming rolls 23 and 23 which operate to form the plastic mass into a core of desired thickness, a top cover sheet 25 being applied to the upper surface of the core by the forming roll 24.

From the forming rolls 23 and 24 the formed board passes over suitable setting conveyors one of which is represented by the reference numeral 23, and it will be apparent that the projection I3 is effective. during the formation of the board stream and during its passage over the setting conveyors, to space adjacent portions of the cover sheet I4 from the setting conveyor so as to form recesses 21 and 2B in the lower surfaceof the formed board on opposite sides of the projection. The setting conveyors 26 support the board stream for a sumcient time t permit the plastic mass or core 2| to set, and

after setting of the core the board stream is advanced to suitable cutting mechanism by means of which the projections I5 and the portions of the board stream immediately thereover are entirely removed. Thus, in Fig. 1, I have shown the cutting means as comprising two pairs of cooperating cutting knives 29 and 30, which are arranged to sever the board stream along the opposite transverse edges of the pro.- jections l5. These cutting knives are of course operated in synchronism with the travel of the board stream so as to sever the board at the proper instant, that is, just as the projection I5 reaches the position shown in Fig. 1 with respect to the knives 29 and 30. As indicated above, a single pair of cutting knives may be used in place of the knives 29 and 30, and these knives may be arranged to sever the board stream along the center lines of the projections I5 thus separating the stream into a plurality of recessed-end boards having ridges or uneven edges along the transverse recessed-ends. Th'ese uneven edges or ridges may then be removed by grinding or sawing so as entirely to; remove the portions of the board stream formed by the projections I5 and to provide uniform recessedend boards.

The character and formation of the board stream as it passes over the setting conveyors is illustrated most clearly in Fig. 3, and the character of the transverse end of the board'produced after the projection I5 has been removed is illustrated in Fig. 4.

Fig. 5 shows the preferred shape of the projections I5 in the sheet I4 .before the plastic mass is applied to the. upper surface of the cover sheet, and although the dimensions of the channel-shaped projections I5 may be varied so that the recesses 21 and 28 produced thereby in the formed board are of suitable depth and length, I have found that a very satisfactory product is obtained if the depth of the recesses indicated by the letter a in Fig. 4 is approximately .03 inch and if the length of the recessed or beveled end indicated by the letter I) inFig. 4 is approximately 1% inches;

In Fig. 6 there is shown a cover sheet 3| having a projection 32 which is formed by embossing or creasingthe sheet 3| to a depth less than the thickness of the sheet. As will be understood by those skilled in the art, embossing or creasing the sheet 3| in this manner provides a continuous horizontal layer of fiber, indicated by the broken.

line 33 in Fig. 6,'which is instrumental in increasing the strength of the embossed or rigid sheet and in resisting deformation or flattening of the projection 32 when the sheet 3| is subjected to tension during the board-forming operation.

In the embodiments of my invention thus far described, the plasterboards formed are of the open or raw-edge type, and it is sometimes desirable -to provide boards of the type having closed edges, which boards areproduced by folding a portion of one of the cover sheets around the plastic mass or core during the board-forming operation. In providing beveled or recessed ends on boards of this type, in accordance with my invention, the bottom cover sheet or liner is formed as shown in Fig. 7, the cover sheet 34. there shown being provided with a continuous channel-shaped projection 35 which extends only board. Thus the edge portions 35 of the linersheet transversely at predetermined intervals to a depth less than the thickness of said sheet to provide outwardly extending channel-shaped pro- J'ections on one surface of said sheet while maintaining a continuous substantially longitudinal fibrous layer, applying a plastic mass to the other surface of said sheet to form a continuous sheet of plasterboard, supporting said plasterboard sheet on a plane surface until said plastic mass has set. said projections supporting portions of said cover sheet in spaced relation to said plane surface to form recesses in one surface of said plasterboard sheet on opposite sides of said projections, and severing said plasterboard sheet along said projections so as to remove said pro-.

jections and form recessed-end plasterboards.

10. In a wallboard apparatus including means for advancing a plastic mass between cover sheets of fibrous material and board-forming means for operating on said cover sheets with the plastic mass therebetween to form a product of desired thickness, the combination of means for periodically embossing the bottom one of said continuously advanced sheets prior to the board-forming operation to form transversely extending linear projections on the outer surface of said bottom sheet, said projections formingrecesses in one surface of the formed board on opposite sides of the projections, and means for severing said formed board along the transverse edges of said projections to remove the projections and form recessed-end boards.

11. In a wallboard apparatus including means for advancing a plastic mass between cover sheets of fibrous material and board-forming means for operating on said cover sheets with the plastic mass therebetween to form a product of desired thickness; the combination of cooperating embossing rolls having intermeshing projections and depressions for transversely embossing the bottom cover sheet as it passes therebetween prior to application of the plastic mass, means for applying a moisture resisting and stifiening medium to the projections on said embossing rolls to reinforce the projections formed on one surface of said bottom cover sheet by said embossing rolls,

said reinforced'projections supporting portions of said cover sheet out of the plane of the surface of the formed board to provide recesses in said surface, and means for severing said formed board along the transverse edges of said reinforced projections to remove said projections and form recessed-end boards.

12. In a wallboard apparatus including means for advancing a plastic mass between cover sheets of fibrous material and board-forming means for operating on said cover sheets with the plastic mass therebetween to form a product of desired thickness, the combination of means for periodically embossing the bottom one of said continuously advanced sheets prior to the board-forming operation to form transversely extending linear projections on the outer surface of said bottom sheet, conveyor means for supporting the formed board until the plastic mass has set, said projections engaging said conveyor means to support adjacent portions of said bottom cover sheet out of the plane of the surface of the formed board, whereby recesses are formed in said surface on opposite sides of said projections, and means for severing said formed board along the transverse edges of said projections after the plastic mass has set to remove said projections and form depressed-end boards.

13. In a continuous process of forming plasterboards by depositing a plastic mass on a bottom cover sheet, folding the edge portions of said sheet about said mass, applying a top cover sheet, forming the plastic mass between said cover sheets and supporting the resulting product on a plane surface until the plastic mass has set, the steps which consist ofembossing the bottom cover sheet at longitudinally spaced intervals before application of the plastic mass to form projections extending transversely across only that portion of the bottom cover sheet which covers the bottom surface of the finished product whereby said edge portions may be folded, and so severing the formed product as to remove the projections after the plastic mass has set and form recessedend boards.

JAMES K. DUNCAN. 

